Combustion heating apparatus and controls therefor



F. B. AUBERT Oct. 6, 1953 COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR 3 Sheets-Sheet 1 Original Filed July 26, 1943 INVENTOR A, ATTORNEY Oct. 6, 1953 F. B. AUBERT 2,654,422

COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Original Filed July 26, 1945 5 Sheets-Sheet 3 @FUEL PUMP m BLOWER INVENTOR FIG. 5 BY .AJ ATTORNEY Patented Oct. 6, 1953 COMBUSTION HEATING APPARATUS AND CONTROLS THEREFOR Fred B. Aubert, Grosse Pointe, Mich. Original application July 26, 1943, Serial No.

496,099, new Patent No. 2,484,602, dated October 11, 1949. Divided and this application September 10, 1949, Serial No. 115,062

6 Claims.

Another object is to provide a heating apparatus having a ram air supply and a blower and means responsive to ram air pressure for stopping the blower upon occurrence of a predetermined pressure.

Another object is to provide a control by which the supply of fuel is increased upon an increase a in the rate of supply of combustion air.

Other objects will become apparent from time to time throughout the specification and claims as hereinafter related.

The invention consists in the improved-control system and device, the cooperative relation of parts and their agroupment in cooperative relation, to be more fully described hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawings to be taken as a part of this specification there are fully and clearly shown several preferred embodiments of the invention, in which drawings:

Figure 1 is a diagrammatic view of th heating apparatus and control system as applied to the heating of aircraft,

Fig. 2 is a diagrammatic view similar to Fig. l but showing another form of control mechanism,

Fig. 3 is a detail diagrammatic view of another form of fuel fiow controlling means,

Fig. 4 is a view of the control mechanism and apparatus as in Fig. 1 but having an electric drive for the control mechanism,

Fig. 5 is a diagrammatic view of another form of control system having an electric drive, and

Fig. 6 is a diagrammatic view of a heating apparatue embodying the feature of the foregoing control systems of control of the fuel in accordance with the supply of combustion air as included in the system of Figs. 1 to 5.

Referring to the drawings by characters of reference, and particularly to Fig. 1, there is shown diagrammatically a combustion heater control system and control mechanism therefor. For a 2 better description of the control mechanism per se the reader is referred to my co-pending application, Serial No. 496,099, now Patent 2,484,602, issued Cctober 1 1949, of which this application is a division,

For actuating and timing the operation of the system there is provided a hand wound spring driven timing motor 8 which may be of the type known on the market as the Minute Minder, manufactured by the Lux Clock Company, New Haven, Connecticut, and which has a combined winding and drive shaft iii extending from the opposite walls or faces of the clock or timer motor casing. The front end portion of the shaft it which projects from the cover of the timer has secured thereon a winding key and stop member cooperable with stops (not shown) which determine the-limits of shaft rotation upon winding and unwinding respectively of the clock spring. A cam disc member H3 is carried on the shaft it and is rigidly connected thereto, as by a set screw or the like, for movement therewith. There is a second shaft 2| which is positioned coaxial with the shaft l9 and which has a projection at one end journaled in a recess in the end of the shaft it. On the shaft 2| there is rigidly secured a second cam disc member 22 for movement therewith. The disc 22 has a slot 24 facing the disc M and receiving the end of a pin 25 carried by and projecting from the disc Hi. The slot 25 may be a cylindrical bore and is sufficiently wider than the pin 25 to provide a lost motion connection between the discs hi and 22 and the shafts i9 and 2| to permit a relative movement therebetween. The extent of lost motion provided is, for the present design, substantially 30 of shaft rotation. A magnetic plate or armature member 26 is fixed to and rigidly carried by the shaft 2| for movementtherewith. Surrounding the shaft 2| adjacent the armature 25 there is a helical coil spring 28 which has one end anchored, to armature 26 and having its other end anchored exterior of the shaft so that the spring 28 tends to rotate the shaft 2| in a clockwise direction facing Fig.1. Positioned adjacent the shaft 2| there is an electromagnet 3| having lead wires 32, 33 and which is cooperable with the armature 2% to provide a means for holding the cam disc 22 against rotation.

Positioned adjacent the cam discs I i and 22 there are a plurality of switch units arranged for operation by said discs. The switches are shown diagrammatically but are preferably toggle spring snap acting switches such as are manufactured by the Arco Switch Company of Cleveland, Ohio.

Two of these switch units designated 31, 38 are positioned adjacent the cam disc 22 and having operating thrust member 39 and 40 respectively operatively engaging the cam disc for actuation thereby. Positioned at opposite sides of the cam disc I4 there are switch units 4|, 42 having thrust members 43, 44 respectively for actuation by the cam disc. Pivoted adjacent the cam disc I4 there is a lever member 41 which abuts the thrust member 44 and which has its free end rebent as at 48 to provide a cam follower portion engaged with the peripheral face of the cam disc I4. The cam disc I4 has a cam or lobe 49 which is operable to engage the cam follower portion 48 and move the lever 41 and thrust member 44 to close the switch 42. For operating the switch 4| there is provided a pivoted cam follower lever 50 engageable with the switch thrust member 43 and terminating at its free end in a cam follower portiton 5| engaging the peripheral face of the cam disc I4. The follower portion 5| is operated by a cam or lobe 52 to actuate the double throw switch of unit 4| by moving the thrust member 43. For operating the switches 3'7, 38 there is provided a pivoted cam follower lever 53 engageable with the switch thrust member 39, 40 and having its free end terminating in a follower portion 55 riding on the peripheral face of the cam disc 22. The follower portion 55 and lever 53 are operated by a cam or lobe 53 on the disc 22 to move the thrust member 39, 40 and actuate the switches 37, 38. The cam 49 extends, facing toward the left of Fig. 1, a distance more than 120 and the cam 52 is spaced from the follower member portion 5| substantially 90, the cam 52 extending clockwise, facing toward the left of Fig. 1, a distance greater than 30. The cam 56 is positioned substantially 120 in a clockwise direction from the cam 49.

In the control circuit, and preferably adjacent the timing mechanism there are a plurality of jack type connections, the plugs or jacks being referred to by the letters A to G and the operating sockets or receptacles being referred to as A to G respectively. The plugs and receptacles would in commercial assembly be carried by cooperating terminal blocks or panels. The jacket terminal A is connected by a lead wire I to the fixed contact I6 of the switch 42 which has the contact of its switch blade 'I'I connected by a lead wire I8 to the switch blade 19 of the double throw switch 4|. The switch contact 80, normally closed by the contact of blade 19, is connected by a lead wire 8| to the switch blade 82 of switch 31. A contact of switch blade 82 is cooperable with a fixed switch contact 83, connected to the lead Wire 32 of the coil 3|. The lead wire 32 is connected by a lead wire 84 to the jacket terminal B. Positioned in the circuit for the holding coil 3| there is a manually operated normally closed switch 85 having a manual push button 81. The fixed contact 88 of the switch 85 is connected to the holding coil 3| by the lead wire 33. The contact of switch blade 89 of switch 85 is connected by a lead wire 90 to the jacket terminal C. The switch 42 has its blade TI and lead wire 18 connected by a lead wire 9| to the jacket terminal D. The normally open fixed contact 92 of the switch 4| is connected by a lead wire 93 to the relay coil 58 of a relay switch 51. From the other terminal of the coil 58 a lead wire 94 connects to the jacket terminal E. The relay switch arm 95 is connected by lead wire 95 to the jacket terminal A and the fixed relay contact 91 is connected by lead wire 98 to the lead wire 8| and switch arm 82 of the switch 31. The switch 38 has its switch arm 99 connected by a lead wire I00 to the jacket terminal F. The fixed contact IOI of switch 38 is connected by a lead wire I02 to the jacket terminal G. A pilot light indicator I03 has one terminal connected by a lead wire I04 to the fixed switch contact I0| and lead wire I02, the other pilot light terminal being connected to ground by a lead wire I05. The receptacle terminals are connected to the source of current supply or to the heating apparatus.

The fuselage or cabin of the aircraft which is to be heated by the heating apparatus is designated I 01. The heating apparatus has a furnace I08 with a combustion chamber I09 having an outlet stack or discharge duct I09 leading to the exterior of the aircraft. Surrounding the combustion chamber I09 there is an air heating jacket or plenum chamber H0 which is supplied with air to be heated from the exterior of the aircraft through an inlet conduit III. The chamber III) has a discharge conduit IIZ for the heated air and which may lead to one or more desired discharge points. Within the combustion chamber I09 there is a liquid fuel capillary feeding member I I3 which is supplied with liquid fuel from a constant level device II4. A constant displacement pump II5 feeds the device 4 through a conduit H6 and draws liquid fuel from a supply tank H1. The pump I I5 is driven by an electric motor I I8 having one terminal connected to ground by a lead wire H9 and having its other terminal connected by a lead wire I to one terminal of a pressure responsive safety switch I2| which acts to open upon the occurrence of excess liquid pressure in the conduit I I6.

From the other terminal of the safety switch a lead wire I22 connects through a low motor speed resistor I23 to the socket terminal B for connection to the jacket terminal B. There are two parallel resistor circuits, one having a low motor speed resistor I23 connected by a lead wire I24 to the socket terminal B which connects to the jacket terminal B. The other parallel circuit has a high motor speed resistor I connected by a lead wire I23 to the socket terminal G connected to the jacket terminal G. In the combustion chamber I09 and cooperative with the fuel feed member I I3, there is a hot wire igniter I 2'! for generating an igniting temperature in excess of 1200 F. The igniting means I21 is connected to ground by a lead wire I28 and has its other end connected by a lead wire I29 to the socket terminal E connected to the jacket terminal E An air temperature safety switch I has a temperature responsive member I3I in heat exchange relation with the jacket IIO and operable to open the safety switch at a temperature of say 170 F. The switch I30 is connected by a lead wire I32 to the socket terminal C connected to the jacket terminal 0. The combustion chamber I09 is supplied with combustion supporting air through a duct I33 which is fed with air under pressure by a blower I 34 driven by an electric motor I or is supplied with air under pressure from an air ram I 35 comprising a branch duct leading to the exterior of the airplane. The blower motor I35 has one terminal connected to ground by a lead wire I3! and has its other terminal connected by a lead wire I38 to one fixed terminal I39 of a double throw air pressure responsive switch I which is responsive to the air pressure in the duct I 33. The air pressure responsive switch arm MI is connected by a lead wire I42 to the socket terminal D connected to the jacket terminal D. The normally Open fixed contact I43 of the air pressure responsive switch is connected by a lead wire I44 to the socket terminal F connected to the jacket terminal F. The foregoing circuits are energized from a source of electric current supply such as a battery I45 preferably having a potential of 24 v. and which has its negative terminal connected to ground by a lead wire I46 and'has its positive terminal connected by lead wire I41 to the socket terminal A connected to the jacket terminal A.

The operation of the control system and heating apparatus just described is as follows: When it is desired to start the heating apparatus to supply heat to the enclosed aircraft space, the winding knob or key II is rotated counter-clockwise facing toward the left of Fig. 1 to the start position at which it engages a stop pin. This rotation of the member I I winds the spring of timer motor 8 for substantially a twenty minute running period and simultaneously rotates the drive shaft I0 and the armature supporting shaft 2| and their respective cams to set position for burner starting operation. Rotation of shaft II) first engages cam 49 with follower member 41 to close the main switch 42 and then, upon 90 of continued rotation which covers a minute timer motor running period, engages cam 52 with follower member 50 to actuate the double throw switch 4| to open the circuit at contact 80 and to close the circuit between blade 19 and contact 32. At the time of closure of switch 42, the lost motion connection by pin and slot 24 has been taken up so that the cam discs I4 and 22 will have simultaneous equal rotation. Winding of the shaft I 0 continues from the point at which follower member 50 drops off of cam 52 for a distance of which is a five minute running interval or period of the motor 8. This additional 30 winding movement of shaft I0 acts to move the cam 56 under the follower member 53, thereby closing the switches 31, 38 and carries or rotates the holding means armature 26 against the force of spring 28 into holding relation to the electro-magnet 3!. Current from the battery I45 will now be supplied through panel terminal members A, A and lead wire 15 to the main switch fixed contact 18, thence through switch blade 11 and lead wires 18, 9I to panel terminal members D, D, thence via lead wire I42 to the switch arm MI and closed contact I39 of the air pressure or ram switch I40, thence via lead wire I38 to one terminal of the blower motor I and thence to ground via lead wire I31. The blower I34 is thus placed in operation to supply combustion air through duct I33 to the combustion chamber I09. Closure of switch 42 also closes the circuit to switch arm 19 of the double throw switch 4i so that circuit is completed from the switch arm to the now closed, but normally open, contact 92 to the relay coil 58 via lead wire 93, thence via lead wire 94 to the panel terminals E, E and via lead wire I29 to the hot wire igniter I21 and thence to ground via lead wire I28. The igniter I21 is therefore energized but closure of the relay switch 51 to supply fuel is dependent upon a sufficient amperage of the current supply, such as to raise the temperature of the igniter I21 above a minimum desired igniting temperature, as above noted. The relay switch 51 will therefore also not be closed if there is a break in the igniter circuit or if the operating amperage for relay coil 58 and igniter I21 is not provided. The closure of switch 51 establishes a circuit from the battery I in shunt 6 with the switch 42 and now open, but normally closed, contact of switch 4|. This shunt circuit leads from the battery I45 through lead wire I41 to panel terminals A, A, thence to relay switch arm 95 via lead wire 96 and from relay switch contact 91 via lead wire 98 to the lead wire 8| and switch arm 82 of switch 31. .Cam 5.6 has closed the switch 31 and the circuit will continue through lead wire 32 to the coil of holding magnet 3I and thence via lead wire 33 to the fixed contact 88 of the burner stopping switch and thence from the burner stopping switch contact 89 via lead wire 90 to panel terminals C, C, and thence to the bonnet temperature safety switch I30 and to ground. Closure of relay switch 51 also completes the circuit through the low motor speed switch 31 via lead wires 32 and 84 to panel terminals B, B, thence via lead wire -I24 through low motor speed resistor I23 and lead wire I22 to the closed fuel pressure safety switch I2I and thence via lead wire I20 to one terminal of the pump motor H8 and thence to ground via lead wire II 9. Fuel and combustion air being supplied and the igniter I21 being at igniting temperature, the heating apparatus will be in operation and the timing motor 8, the winding key II having been released, will also be operating or running to rotate the shaft I0 clockwise facing toward the left of Fig. 1. When the ignition period has elapsed, preferably for five minutes duration, the cam 52 will have released follower member 50 so that arm 19 of switch 4| will move back to initial position, closing the circuit of contact 30 and opening the circuit of contact 92. The switch M, as are the other switches, being snap acting, the interchange of circuits from contact 92 to contact 80 will not interfere with burner operation. Breaking of oirciut at contact 92 will deenergize the relay coil 58 and igniter I21, thereby opening the relay switch 51, but the closure of arm 9 with contact 80 will maintain the continued operation of the pump I I8, since the contact 30 and the relay switch 51 are in shunt circuit. As long as combustion air pressure in the supply duct I33 and therefor in the branch duct I33 is below the pressure for which the ram switch I40 is set, the heating apparatus will continue in operation at low fuel consumption due to low speed pump motor operation which is sumcient to supply fuel I in accordance with the air supplied by the blower I34.

When the quantity of air supplied to the combustion chamber through duct I33 exceeds the quantity for a proper fuel air ratio, the increased pressure of the combustion air in the duct I33 and branch duct I33 will actuate the ram switch I40 tomake circuit between the arm MI and the contact I43. This increased air pressure for actuating the switch I40 will result from the speed of the aircraft in flight. Closure of the circuit between arm MI and contact I43 will break the blower motor circuit at switch contact I39 and will complete the high speed fuel pump motor circuit as follows: From contact I43 via lead wire I44 to the panel terminals F, F, thence via lead wire I00 to switch arm 99 of switch 38 and its engaged contact I9l, thence via lead wire I02 to the panel terminals G, G to lead wire I26 and through the high motor speed resistor I25, lead wire I22 and closed fuel pressure switch I2I to the motor II8 via lead wire I20. Closure of contact between arm MI and contact I43 will also complete the circuit through closed switch 38 to the indicator pilot light I03, connected by lead wire I04 to contact IM and lead wire I02 and connected to ground by lead wire I05. As long as the aircraft continues in flight and the air pressure in ducts I33 and I35 is greater than the pressure created by the blower I34, the heating apparatus will continue to operate at high fuel supply.

Irrespective of whether burner is operating at high or low fuel consumption, the operation of the heating apparatus can be stopped by the manual switch 85. When the push button 81 of this switch is moved inward, the switch 85 will be opened by movement of arm 89 out of engagement with contact 88, which will break the circuit through the holding magnet coil 3I. Deenergization of coil 3| will permit the spring 28 to move the armature 26 quickly toward the position shown in Fig. 1, due to the lost motion of pin 25 in slot 24. Cam 56 will move with initial movement of armature 26 and out from under follower member 53 so that the switches 31 and 38 will be opened, which will break both the low speed and the high speed fuel pump motor circuits. The release of the armature 26 will reinstate and release for continued operation the timing motor 8. Cam disc I4 will now again be rotated clockwise facing Fig. 1 from its actuated position. The 90 of cam movement from the actuated position occupies a time period of I5 minutes and when this time period or interval has elapsed, the cam 49 will move out from under the follower member 47 so that the switch arm ll of switch 42 will break circuit with the contact member I6, thereby breaking the circuit to the ram switch arm I4Ii If the aircraft is on the ground or its air speed has decreased, so that the ram switch I40 breaks circuit at contact I43 and makes circuit at contact I39 at the time when the burner stopping button 8? is actuated, then the blower motor I35 will be maintained in operation during the time interval prior to movement of cam 49 from under the follower member 4'! and consequent opening of switch 42. Accordingly, there will be at least a predetermined period of supply of scavenging air to the combustion chamber I 09 immediately following the stopping of the fuel pump II5. It will be apparent that if the pump H5 is stopped during flight by operation of switch 35, that scavenging air will be supplied by the speed of the aircraft through branch duct I36 and the blower motor I35 will not be placed in operation, but if the pressure of the combustion air decreases below the pressure supplied by blower I34 prior to or after landing of the aircraft and within the 15 minute interval, then the blower I34 will immediately be placed in operation to continue the supply of scavenging air. Should the temperature of the air jacket or plenum chamber exceed the desired safety limit of 170 F., the safety switch I30 will be opened, thereby breaking the circuit of the holding coil I3I, thereby stopping the burner and establishing the scavenging period in the same manner as opening the switch 85 with which the switch I30 is in series circuit.

Referring to Fig. 2, a different form of cam and holding means armature and a different circuit arrangement for the fuel pump motor is shown. The operation of this control system and apparatus will be apparent from the above description, taken in connection with the following. When the timing means motor 200 is set or wound by operation of the key or knob 20I, the cam 202 will engage the switch operating follower member 203 to close the main switch 204. Upon continued winding of the motor, the cam 205 will engage the switch operating follower member 206 to actuate the switch arm 20'! of the double throw switch 208, thereby breaking circuit at the inlet closed contact 209 and making circuit at the normally open contact 2I0. Simultaneously with the engagement of cam 202 with the follower member 203, the lost motion pin 2I I will engage the end of the lost motion slot 2I2 to initiate movement of the cam member 2 I 3. When the cam member 2I4 carrying cams 202 and 205 has been moved sufiiciently to carry the cam 202 a distance equal to say twenty minutes of timing motor running time beyond or to the left of follower member 203, the cam 2I5 of member 2 I3 will engage and move under the cam follower 2I6, thereby to close the switch 2I'I. Simultaneously with closure of switch 2I'I, the holding means armature 2I8 carried by the cam member 2I3 will be moved into magnetic holding relation relative to the electro-magnet 2I9. Closure of the main switch 204 will complete a circuit from the battery or current supply source 220 via lead wire 22I to the lead wires 222, 223 leading respectively to the fixed contact of switch 204 and to the switch arm 224 of the relay switch 225. From the closed switch 204 a lead wire 226 connects through the panel terminals to a lead wire 22'! connected to the switch arm 228 of combustion air pressure responsive or ram switch 229 and thence through the normally closed contact 230 via lead wire 23I to the motor 232 of the combustion air blower 233 and to ground via lead wire 234. Closure of main switch 204 also completes the circuit to the coil 235 of relay switch 225 and to the hot wire igniting means 236 as follows: From main switch lead wire 226 via lead wire 23'! to switch arm 20'! in contact with a now closed but normally opened contact 2I0, thence via lead wire 238 to one terminal of the coil 235, thence via lead wire 239 to panel terminals and via lead wire 240 to one terminal of the ignition wire 236, and from the other ignition terminal via lead wire 24I to ground. The relay switch 225 is in shunt circuit with the now open, but normally closed, switch contact 209 and closure of relay switch 225 by energization of its coil 235 completes a circuit from the battery 220 through relay arm 224, to relay contact 242, thence via lead wire 243 to low motor speed resistor 244 connected in lead wire 245, which is connected to lead wire 246, leading to one terminal of the cam operated switch 2I'I. From the other terminal of switch 2I'I, the lead wire 247 connects to panel terminals from which lead wire 248 connects to one terminal of the high motor speed resistor 249 having its other terminal connected by lead wire 250 to the switch arm of the fuel pressure responsive safety switch 25I from which a lead wire 252 connects to one terminal of the fuel pump motor 253 having its other terminal connected to ground by lead wire 254. The resistors 244 and 249 are in series circuit to provide low speed motor operation for a low rate of fuel supply by the fuel pump 255 to the constant level valve 256 which supplies the capillary oil feeding means 257 in the combustion chamber 258 of the heating apparatus 259. Connected to the lead wire 241 from switch 2!! there is a lead wire 260 connected to one terminal of the electromagnet 2I0 from the other terminal of which extends a lead wire 28! to the contact 262 of the burner stopping switch 263, having its switch arm 264 operable by the push button 265. From the arm 264 a lead wire 266 connects to the panel 9 terminals and a lead wire 26? connects to the fixed contact of the bonnet temperature responsive safety switch 268 having its temperature actuated arm connected to ground by lead wire 269. From the foregoing, it will be apparent that the heating apparatus is now in operation, the knob 2ll| having been released, fuel being supplied by the pump 255 and combustion air by the blower 233, the combustible mixture being ignited by the hot wire igniter 236, assuming, of course, that the proper amperage was supplied to the relay coil 235 as above described for Fig. 1. When the timing means Ztil has run for the desired ignition period of five minutes, then the cam 205 will move out from under the follower member 2%, so that the switch 2518 will be actuated to break circuit at contact 210 and to make contact at 209, the cam member 2H3 being held by electro-magnet 2l9 against the force of the return spring 275% position with cam 215 holding the switch 2!? closed by reason of the permitted lost motion between pin 2!! and slot 2l2. Closure of switch 209 establishes a circuit from the battery 2% in shunt with the relay switch 225, via a lead wire 2?! which connects the contact 2% to the lead wire 225 of the resistor 24 3. When the cam 295 moves out from under the follower member 206 the end well of the lost motion slot 2l2 will be engaged by pin 2| l, thereby stopping further running of the timing means motor 2%, and the burner will continue in operation at low fuel consumption as long as the pressure in air supply duct 2'52 does not exceed the air pressure provided by the blower 233. energizes the relay coil 235 and the hot wire igniter 236. When the aircraft supplied by the heating apparatus 259 is in flight, so that the pressure of the air supplied to duct 2l2 through the branch duct 213, opening to the exterior of the aircraft, exceeds the pressure provided by the blower 233, then the ram switch 229 will be actuated to break circuit at the contact 239 and to make contact at the normally opened contact 2M so that current will flow from the switch f this circuit at contact 214 short circuits the low c speed resistor 2M5 so that the speed of motor 253 will be increased to provide the necessary increased supply of fuel to compensate for the increased air supply due to the higher air pressure in the combustion chamber supply duct 2T2. Closure of the circuit at ram switch contact 2*!!! also completes the circuit from lead wire 216 through lead wire 2?? to the pilot light indicator 213, which is connected to ground. As in connection with Fig. 1, discontinuance of burner operation is effected by depressing the push button 265 which opens the burner stopping switch 2263, thereby deenergizing the holding magnet 239 so that the spring 21!? retracts the cam 2l5 from its position holding switch 2!! closed and also moves the end wall of slot 2 l2 out of holding relation to the pin 2H so that the timing motor 296 is permitted to continue its operation of returning cam 292 to the position shown in Fig. 2. This time period of reinstated operation of the motor 2% extends over a minute period prior to movement of cam 202 out of holding relation to minimum switch 2M, so that during this time period the blower motor 232 will be energized to supply scavenging air to the combustion cham- Breaking of circuit of contact 2!!) dein her 253 as the pressure in the duct 2'52 is below the pressure provided by the blower 233, all as above described in connection with Fig. 1.

In Fig. 3 there is shown a modification of the fuel supplying means of Figs. 1 and 2. In this Fig. 3 the control of fuel supply is by means of electrically operated or solenoid valves 2%, 28f controlling flow from a manifold or conduit 282 to a pipe or conduit 283 which feeds the fuel distributing means in the combustion chamber. The valve 28% may be connected to the lead wire I2 or Fig. 1 leading from socket terminal B connected to jacket terminal B and controlled by switch 3'3. The valve 28! may be connected to return wire 526, connected to socket terminal G, which is connected to jacket terminal G having its circuit controlled by cam switch 38 and the air pressure responsive switch Hill. Thus, for blower air supply to the combustion chamber the fuel will be fed through valve 2613 alone and for night or high combustion air pressure fuel will be supplied through both of the valves 2% and 28!.

In Fig. 4, the timing motor is electrical and the control device and system is constructed and arranged substantially as above. When it is desired to start the heating apparatus in operation, the control arm 3% is rotated through 120 to the start position, which rotates shaft 3i]! having fixed thereon a cam disc or member 392 with a main switch operating cam 3M and a relay and igniter controlling cam 304. The cam member 3% is coupled to a cam disc or member 385 by a lost motion pin and slot connection 3%, such that the shaft 38! is movable relative to the shaft 3t? to which the member 395 is fixed. Rotation of shaft 39! to the start position first moves cam 363 into operative engagement with follower member 338 to close the main switch 30%). Upon rotation of cam member 302 through substantially from the point of operation of switch 369, the cam 3M engages follower member 3m to actuate the double throw switch 3!! to break contact at the normally closed contact 312 and to make contact at the normally open contact 313 at the time of closure of switch 309. The lost motion between cam members 302 and 305 is taken up so that the member 385 is rotated with the member 362 and so that upon substantially 30 of shaft rotation upon operation of follower member Bill, the cam '3M of cam member 395 engages its follower member 355 to close the low speed fuel pump switch BIB, the high speed fuel pump switch Bi? and to open the timing motor switch 3 it. As in the device of Fig. l, the rotation of shaft 3M also rotates the holding means armature tie against the force of its return spring 320, so that the armature 3l9 is positioned in holding relation to its electro-magnet 32! upon operation of follower member 315 by cam Bis. Rotation of the starting lever 505i to the start position closes the circuit from the battery or source of current supply 322 to the combustion air blower motor 323, the circuit being from the battery 322 (which is connected to ground) through lead wire 324 to the fixed contact of main switch 389 and from the movable switch contact via lead wire 325, through the normally closed contacts of the combustion air pressure responsive or rain switch 326 and lead wire 32'l to one terminal of the blower motor 323 and from the other blower motor terminal via lead wire 328 to ground. Closure of switch 369 also closes circuit from lead wire 325 via lead wire 329 to the movable contact or switch arm of the double throw switch 3! I engaging the now closed, but normally opened, fixed contact 3|3, thence via lead wire 330 to one terminal of the coil 33! of relay switch 332 and from the other coil terminal via lead wire 333 to one terminal of the hot wire igniter 334 having its other terminal connected to ground. Energization of relay coil 33l actuates the relay switch arm 335 to engage the fixed relay contact 336, thereby completing a circuit in shunt with the main switch 309 and the normally closed. contact 3| 2 of switch 3| I. This shunt circuit leads from the battery lead wire 324 via lead wire 33'! to the switch arm 335 and thence through contact 336 and lead wire 338 to the movable contact of low speed switch 3; and thence via lead wire 330 to lead wire 340 which is connected to one terminal of the fuel pump motor 34! and contains a variable resistance 342. The other terminal of the fuel pump motor is connected to ground by a lead wire 343. From the lead wire 339 a lead wire 344 connects to one terminal of the coil magnet 32! which has its other terminal connected by a lead wire 345 to the fixed contact 345 of the manual burner stopping switch 34?, having an operating rod or push button 348. The switch arm 349 of the switch 341 which is operated by the button 348 is connected by a lead wire 350 to ground. The relay switch 332 also controls the electric timing motor 351, the circuit being as follows: From the battery lead wire 324 via lead wire 352 to relay switch arm 353 engaged with switch contact 354 and thence via lead wire 355 to one terminal of the motor 351' and from the other motor terminal via lead wire 353 to ground. The motor 35! is connected through a reduction gear train 351 to a clutch member 358 cooperable with a friction spring clutch member 359 rigid with the shaft 30 l. Assuming that the igniter 334 is properly energized as described above in connection with the foregoing systems, the burner will be in operation at low fuel supply and will be supplying heated air to the desired supply points and the timer motor 35! will be rotating the cam member 302 toward igniter stopping position, the cam member 305 being held against rotation by the armature 3L9 and its holding magnet 32L This low fuel supply operation of the burner will continue as long as the combustion air pressure is not in excess of the pressure supplied by the blower 323. When the combustion air pressure exceeds that supplied by the blower 323, such as will result from the aircraft in flight, then the ram switch 325 will be actuated to break contact between lead wires 325 and 32? and to make contact between lead wire 325 and lead Wire 350 leading to the high speed fuel motor switch 3! 1, which is held closed by the cam 314. From the closed switch 3|! current will flow through the lead wire 38 I to the adjustable contact 362 of the resistor 342, thereby shunting out a part of the resistor 342 and reducing the resistance in the fuel pump motor circuit which will result in increasing the speed of the fuel pump and accordingly the supply of fuel to the burner. As long as the increased air pressure continues, the increased supply of fuel will continue. When the combustion air pressure decreases to the pressure created by the blower 323, then the ram switch 326 will again place the blower 323 in operation by closure of contact between lead wires 325 and 321, which will also break the circuit through switch 3 l 7 so that the fuel pump motor will again be operated at low speed. When it is desired to 12 stop further operation of the burner, irrespective of whether the aircraft is in flight or on the ground, that is, irrespective of the ram switch 326, the manual stopping switch 341 is actuated by the push button 348 which will break the circuit through the holding magnet 32!. Release of the armature 3I9 by the deenergization of magnet 32l will permit spring 320 to rotate cam 3! from its holding relation to follower member 3|5 due to the lost motion pin and slot connection 306. Release of the follower member 3l5 will result in the opening of switches 3I6 and 3H, thereby deenergizing the fuel pump motor 34| and will close switch 318, thereby completing a shunt circuit to the timing motor 35! as follows:

From the ram switch lead wire 325 through lead wire 353 to the fixed contact of switch 318 and thence through the switch arm via lead wire 364 to the lead wire 355, connected to the timing motor 35L This will reinstate operation of the motor 35!, thereby reestablishing rotation of cam member 302 to provide a predetermined time period prior to opening of main switch 300 controlling the blower 323. When the motor 35l has operated through a period of say 15 minutes for scavenging of the combustion chamber, either by operation of blower 323 or by the increased pressure of flight created combustion air, then the cam 303 will move out of holding engagement with follower member 308 and switch 309 will be opened. The opening of switch 309 breaks the circuit through switch 3|8, thereby deenergizing and stopping the timing motor 35l in the stop position of operation or setting knob or handle 300.

In Fig. 5 another form of electrically driven timing motor control is shown. In this figure a single operating cam rotatable in one direction only is employed and the manual reverse cam operation for starting of the heating apparatus is eliminated. When it is desired to start the burner of the heating apparatus in operation, the main switch 400, which is a double throw manual switch having an operating extension or lever 40l operatively connected to its switch arm 402 is moved to the left facing Fig. 5 to engage the switch arm contact with the fixed switch contact 403, so that a circuit from the battery or source of current supply 404 is completed through the lead wire 405 to and through the switch 400 and thence through lead wire 406 to one terminal of the coil 40! of the timin motor controlling relay switch 408. From the other terminal of coil 401, a lead wire 409 extends to the switch arm 4l0 of a normally closed cam operated switch 4. From the fixed contact 4|2 of the snap acting switch 41! a lead wire 4l3 connects to one terminal of the hot wire igniting means 4l4 which has its other terminal connected to ground. Operation of switch 400 to close circuit through its contact 403 therefore energizes the igniter M4 and actuates the relay switch 408, provided the igniter circuit is complete and the current supply is sufficient to actuate the relay switch 408 as described above in connection with Fig. 1. The operation of relay switch 403 pulls the relay switch arm 4l5 into engagement with the fixed relay contact M6 to close the circuit of the timing motor 4|! as follows: From main switch lead wire 405 through lead Wire M8, to relay switch arm M5 and its engaged contact M8 to lead wire M9, connected to the closed contact 420 of the normally closed cam operated snap acting switch 42L having its movable switch arm 422 linked for movement in unison with switch arm 4| 0.

13 From the switch arm 422 a lead wire 423 extends to one terminal of the timing motor 4H, which has its other terminal connected to ground by a lead wire 424. Energization of timing motor 4H drives its cam member 425 to move the cam clockwise in the direction of the arrow facing Fig. 5, to move cam 42% out of holding relation to the cam follower thrust member 42'! so that the snap acting switches 428 and 429 are moved to closed position. Closure of the blower control switch 423 completes a circuit to the combustion air supplying blower motor 430 through the combustion air pressure responsive or ram switch 43! as follows: From battery lead wire 405 through lead wire 432 to the fixed contact of switch 428, and from its cam operated switch arm 433 via lead wire 434, to the normally closed contacts of ram switch 43! and therethrough to the lead wire 435 connected to one terminal of the blower motor 435 having its other terminal connected to ground by lead wire 433. The main switch 400, upon engagement with its contact 403, also controls the motor of the fuel supply pump 43'! through the intermediary of relay switch 438. Engagement of switch arm 402 and contact 403, which closes the circuit from the battery 404 to lead wire 4%, energizes the relay switch coil 439 having one terminal connected by lead wire 440 to the lead Wire 406 and having its other terminal connected to ground by lead wire 44!. The cam operated blower switch 428 also controls the energization of the fuel pump motor 43! as it is in series circuit with the low speed fuel pump switch arm 442 by lead wire 443, connected to lead wire 434. Closure of relay switch 433 en- 7 gages the arm, 442 with fixed contact 444, thereby completing the circuit to one terminal of the pump motor 431' via lead wire 445 having therein the low speed resistance 443, the other terminal of the pump motor being connected to ground by lead wire 44?. The heating apparatus will now be in operation at low fuel consumption to supply the desired amount of heat in accordance with the combustion air supply provided by the blower. Upon increase in the pressure of the combustion air above the pressure provided by the blower, such as will occur when the aircraft is in flight,

the ram switch 43! will break circuit between the blower motor supplying lead wires 434 and 435 and will make circuit from the lead wire to the lead 443 connected to the switch arm 449 of relay switch 438 and movable in unison with the switch arm 442. Since the switch arm 449 is in engagement with. iii- E61 relay contact 453, the circuit will be completed from lead wire 44% to the lead wire.

35! which connects to the adjustable contact 452 of the resistance 446, thereby shunting out a portion of the resistance 443 to increase the speed of the fuel pump motor 437, inorder to provide the necessary quantity of fuel for a proper fuel air mixture with the increased combustion air supply.

The cam member 425 has been rotating at a predetermined rate, preferably a 20 mir .ite cycle, and when the cam 423 has been rotated through 90 it will, at the end of the five minute period, engage the follower thrust member 453 to oper ate the arms 422 and 4553 of the switches 225 and i! 5 respectively to break the circuit of the timer motor 4!? and of the igniter M4. Although the circuit to the timing motor 4! is broken at the relay switch 433 upon opening of switch 4H which deenergizes the relay coil the switch s2: provides a safety control to assure stopping of the timing motor 4!? in the event relay switch 3 4518 should fail to open. Upon operation as above described, either at low or high fuel, consumption will not be affected by the time of operation of follower member 453 by cam 426. When it is desired to stop operation of the burner, the switch operating member 463i is moved to the position shown in this Fig. 5 in which switch arm 332 engages the fixed contact 454 so that the timing motor 4i! is reenergized from the battery see through the following circuit: From switch contact 454, through lead wire 455 to the closed cam switch 429 and thence via lead wire to the timing motor lead wire 423. Accordingly, if during the interval of reinstated timer motor operation the combustion air pressure has decreased below the predetermined blower pressure at which ram switch see remakes circuit between lead wires 434 and 335, the blower motor 436 will again be placed in operation to provide scavenging air for the combustion chamber. Upon the termination of the reinstated operating period of 15 minutes of the timing motor M1, the cam 426 will engage the follower member 42! to open the cam switches 423 and 329 to break the circuits of and stop the blower motor 433 and the timing motor til respectively and halting or stopping the cam 423 in its position for the start of another burner heating period when desired.

In Fig. 6 the heating apparatus is shown as having a multispeed combustion air blower and as having high frequency spark ignition for the combustible fuel and air mixture such as disclosed in my oo-pending joint application with De Loss E. Scott, Serial No. 478,600, filed March 10, 1943, now Patent No. 2,444,239, granted June 29, 1948. In this form of the invention, the main switch etc may be a temperature responsive automatic switch having 'a bimetal operated element 5! for actuating a plurality of switch contacts, namely a low speed contact 532, an intermediate higher speed contact 583 and a high speed contact 534 which are cooperable respectively with fixed contacts 535, 5% and sci. The blade 58! and its contacts are connected to a source of current supply via lead wire 583. Upon demand for heat or operation of the heating apparatus, the contact 562 is moved into engagement with the fixed contact 5435, thereby completing a circuit through lead wire 5% to the low motor speed resistor 5N) connected to the lead wire 5!! of one terminal of the combustion air blower motor hi2 having its other terminal connected by lead wire 513 to the return wire 5M connected to the source of current supply. Operation of the blower 5w by the motor E12 will supply combustion air under pressure through the air supply duct 5!% to the combustion chamber- Ell. The engagement of contacts 532 and 585. will also close the circuit to the coil 558 of relay switch 5!?) controlling the burner ignition means 52%, the coil being ener ized through lead wire 52 connecting the coil to the lead wire 53! and via the lead wire 522 extending from the coil to the return wire M4. The relay switch 5E9 is connected. by lead wire 523 to the current supply wire 538 and to one terminal of the primary coil of a current supply transformer 524 by a lead wire 525, the other terminal of the transformer primary coil being connected to the return wire 554 bya lead wire 52%. Therefore, the high frequency spark ignition means 526 will be energised simultaneously with the energization of the blowor motor 5!'2, with a resulting micro amperage radio frequency high voltage spark discharge from the end or tip 521 of the spark discharge electrode 528. Engagement of contacts 502 and 505 will also energize the motor 529 of the fuel supply pump 530 discharging fuel from a fuel tank not shown to and through the fuel nozzle 53| into the combustion chamber 5|1, the circuit of motor 529 being as follows: From the lead Wire 509 on the switch controlled side of the resistor 5 a lead wire 532 connects to the switch arm 533 of a combustion air pressure responsive or ram switch 534 having a low speed contact 535, intermediate higher speed contact 536, and a high speed contact 531. At low combustion air pressure resulting from low blower motor speed, the pressure responsive member 538 of switch 534 will be holding the switch arm 533 in engagement with contact member 535 so that the current supply to the return wire 539 of the pump motor 529 will be through the low speed resistor 540 and from the other motor terminal via lead wire 54| to the return line wire |4. If the temperature should now decrease irrespective of operation of the heating apparatus, the switch 590 will move contact 593 into engagement with contact 506, thereby shunting the resistor Em and supplying current to the blower motor 5|2 from supply line wire 508 through intermediate motor speed resistor 542 to the motor lead wire 5| I. The increased blower speed resulting from the cutting in of the lower resistance resistor 542 will increase the combustion air pressure and the quantity of air discharging through the duct 5|$ to the combustion chamber 5|1, thereby actuating the responsive member 538 of switch 534, so as to move switch arm 533 into circuit making engagement with the fixed switch contact 536. This will cut out the resistor 540 and establish the circuit to the motor lead wire 539 through the intermediate or lower resistance resistor 543, so that the proper ratio of fuel and air in increased quantity per unit of time will be supplied to the combustion chamber 5|1 to increase the heat supplied by the heating apparatus. If the contacts 504 and 501 of the switch 500 are now closed as by a further drop in temperature of the ambient medium affecting switch 500, then the resistors 5|0 and 542 will be shunted by a lead wire 544 connecting the switch contact 501 to the motor lead wire 5| with the result that the blower motor 512 will be operated at its highest speed, thereby to further increase the pressure or quantity of air discharged through the duct 5|3 to the combustion chamber 5|1. This further increased air pressure in the duct 5H5 will act on the switch responsive member 538 to move the switch arm 533 into electrical engagement with the high speed contact 531, so that the resistors 540 and 543 will be shunted out of the circuit of motor 529, the motor now being supplied with current from contact 531 by lead wire 545 to lead wire 539. This increased motor speed will increase the speed of the pump 530 so that the fuel supply will be increased in accordance with the increased supply of air through duct 5|6 in order to provide the desired combustible ratio of fuel to air at a further increased quantity per unit of time, thereby proviidng a further increased supply of heat by the heating apparatus. It will be apparent that as the heating apparatus raises the temperature of the ambient affecting switch 500 so that the contacts 504 and 501 and then the contacts 503 and 506 are separated, that the reverse operation of the burner will occur, cutting down the speed of the fuel pump in accordance with the decreasing speed of the blower motor and that when 16 the switch 500 is satisfied and contact 502 is separated from contact 505, that the pump and blower motors will be deenergized and the relay switch 509 will be opened to deenergize the ignition means 52 0'.

It is to be understood that the ignition means of Fig. 6 could be utilized in the control systems of Figs. 1, 2', 4 and 5 if the safety feature of the series circuit arrangement of the relay coil and hot wire igniter were considered unnecessary and that the ignition means 520 of Fig. 6 could be utilized in the systems of Figs. 1, 2, 4 and 5 with the safety means disclosed in the above mentioned co-pending application as another method of accomplishing the assurance of proper ignition means operation.

This application is a division of my co-pending application Serial No. 496,099, filed July 26, 1943, now Patent 2,484,602, issued October 11, 1949.

What is claimed and is desired to be secured by Letters Patent of the United States is:

1. A heating apparatus for aircraft comprising a combustion chamber having an air inlet, a blower for supplying air to said inlet, a circuit for said blower, a duct adapted to lead to the exterior of the aircraft for supplying air to said inlet by flight-created air pressure, electrically controllable means to supply fuel to said chamber at a low rate and at a higher rate, electric ignition means for the fuel supply to said chamber, a switch controlling the circuits of said blower and of said ignition means, a relay switch having its coil controlled by said last-named switch, said relay switch controlling said fuel supply means for said low rate, and means including a pressure operated switch responsive to air pressure in said duct and controlling said fuel supply means to supply fuel at said higher rate upon occurrence of a high air pressure in said duct.

2. In an aircraft heating system having a heater of the sealed combustion type, and having a scoop or ram and a blower for supplying air to the heater, the combination of a housing connected to said scoop or ram, to the outlet of said blower and to the inlet of said heater, a member having a range of movement and movable toward one limit of its range in response to the pressure of the air flowing from said scoop or ram and yieldably biased in the opposite direction, and a control device actuated by said movable member and operative to stop and start the blower, said control device being so actuated for starting the blower when the pressure from the scoop or ram falls below a predetermined value and permits said member to move in said opposite direction.

3. In the combination defined in claim 2, said control device being actuated by said movable member to stop the blower when the pressure of the air flowing from the scoop or ram rises above a predetermined value and said member responds to said pressure by movement toward said one limit of its range and beyond a predetermined point.

4. In a vehicle carried heating system having a combustion type heater and having a scoop or ram and a blower for supplying air to the heater, the combination of a housing connected to said scoop or ram, to the outlet of said blower and to the inlet of said heater, a member having a range of movement and movable toward one limit of its range in response to the pressure of the air flowing from said scoop or ram and yieldably biased in the opposite direction, and a control device actuated by said movable member and operative to stop and start the blower, said control device be- 1? ing so actuated for starting the blower when the pressure from the scoop or ram falls below a predetermined value and permits said member to move in said opposite direction.

5. In a movable vehicle, a heating apparatus comprising a combustion chamber having air and fuel inlets, means for supplying air to said chamber; said air supply means comprising an air supply duct extending to the exterior of the vehicle in the direction of vehicle movement to receive ram air pressure and an electrically operated blower, each connected to said air inlet; a circuit for energizing said blower, a normally closed switch in said circuit for effecting energization of said blower, and pressure responsive means positioned for response to vehicle speed generated ram air pressure in said duct and operable to open said switch to stop said blower when ram air pressure increases above a predetermined value.

6. In a movable vehicle, a heating apparatus comprising a combustion chamber having air and fuel inlets, means for supplying air to said chamber; said air supply means comprising an air supply duct extending to the exterior of the vehicle for receiving ram air pressure and an electrically operated blower, each connected to said air inlet; means to supply fuel at different rates to said fuel inlet, pressure responsive means positioned for response to air pressure in said duct and operable to start said blower when rain air pressure falls below a predetermined value, and means operated by said pressure responsive means in response to pressure above said predetermined value to cause said fuel supply means to supply fuel at an increased rate.

FEED B. AUBERT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,359,042 Doble Nov. 16, 1920 1,562,663 Strong Nov. 24, 1925 1,583,238 Scudder May 4, 1926 1,835,611 Page et a1. Dec. 8, 1931 1,862,690 Macrae et a1 June 14, 1932 1,923,614 Clarkson Aug. 22, 1933 2,397,987 Senninger Apr. 9, 1946 2,400,117 Holthouse May 14, 1946 2,410,537 Wait Nov. 5, 1946 2,418,566 Arnhym Apr. 8, 1947 2,428,078 Heymann Sept. 30, 1947 

